Motor control system



Jan. 9, 1940. Q H|NE$ 2,186,785

MOTOR CONTROL SYSTEM Filed Feb 23, 1939 R 12 i 9 1p [4 4i 575 52 I B 6.-L-F 09 J04 1029 F B C INVENTOR H15 ATTORNEY Patented Jan. 9, 1940UNITED STATES MOTOR CONTROL SYSTEM Claude M. Hines, Pittsburgh, Pa.,assignor to The Union Switch & Signal Company, Swissvale, Pa., acorporation of Pennsylvania Application February 23, 1939, Serial No.257,853

10 Claims. (01. 172-179) My invention relates to a motor control systemand particularly to an improved system adapted to be employed to controlthe motor for moving a railway track switch.

In some locations it is desirable to employ in the relays or otherdevices controlling the energizing circuit of the switch motor metal tometal contacts.

However, because of the relatively heavy currents present in thecircuits controlled by these contacts, there is a possibility that inservice the metal to metal contacts may fuse together and fail toseparate, and thus fail to interrupt the circuit which they control. Ifthis occurs, it may result in failure of the equipment to operatein theintended manner, and might result in injury to the motor.

It is an object of my invention to provide an improved motor controlsystem incorporating means to verify separation ofthe neutral contactsof a relay employed to control the motor.

'A further object of my invention is to provide an improved system ofthe type described and incorporating means operative to prevent furtheroperation of the motor in the event of failure of the contacts of themotor control relay to separate as intended.

Another object of my invention is to provide an improved control systemfor the motor for operating a railway track switch, the control systememploying a polarized relay having both neutral and polar contacts forcontrolling the circuit of the switch motor to effect movement of theswitch in one direction or the other, the

system incorporating auxiliary means fOr'interrupting the circuit of theswitch motor in the event of failure of the neutral contacts of thepolarized relay to separate in the intended manner.

A further object of my invention is to provide an improved switch motorcontrol. system of the type described, the system incorporating anauxiliary relay separate from the polarized switch motor control relayand controlling the circuits of. the winding of the polarized relay, thecircuit of the winding of the auxiliary relay being controlled by theneutral. contacts of the polarized switch control relay in such mannerthat on a change in the polarity of the current supplied to the circuitsof the windings of the polarized relay and of the auxiliary relay, thewinding of the auxiliary relay cannot thereafter be energizecl unlessthe neutral contacts of the polarized relay become released.

Another object of my invention is to provide an improved motor controlsystem employing a first and a second relay to control the circuit ofthe motor, the first relay being provided with metal to metal contactsand the second-relay being provided with infusible contacts, the con- 6-trol system being arranged so that the first relay normally serves tointerrupt the motor circuit, and so that the second relay will; operateto interrupt the motor circuit if the first relay fails to do so.

A further object of my invention is to provide an improved motor controlsystem incorporating a polar relay and a neutral relay for controllingthe motor circuit, the polar relay having metal to metal neutralcontacts. the neutral relay having infusible contacts, the controlsystem being arranged so that the neutral contacts of the polar relaynormally serve to interrupt the motor circuit, and so that the contactsof the neutral relay will interrupt the motor circuit if the contacts ofthe polar relay fail to do so, the system also being arranged so that ifthe neutral contacts of the polar relay fail to separate when theyshould, the contacts of the neutral relay will thereafter remainreleased and will maintain the motor circuit interrupted.

Another object of my invention is to provide an improved switch motorcontrol system.

Other objects of my invention and features of 30 novelty will beapparent from the following description taken in connection with theaccompanying drawing.

I shall describe one form of apparatus embodying my invention and shallthen point out 35 the novel features thereof in claims.

In the drawing the single figure is a diagram of a motor control systemembodying my invention.

Referring to the drawing, there is shown there- 0 in a railway trackswitch W which is movable between a normal and a'reverse position bymeans of an electric motor M. The circuits of the motor M are controlledby a polarized switch control relay WR, an auxiliary slow releasing new45, tral relay WRP, and an overload relay OR.

The windings of the relays WR and WRP are energized by current suppliedover control wires l0 and l I, while means is provided to selectivelysupply current of one or the other relative po- 50 larity to the controlwires. As shown in the drawthere is a switch control lever L which ismovable between a normal and a reverse position. The lever L hasassociated therewith contacts l2 and 14 which are constantly connectedas to terminals B and C, respectively, of a battery i5.

When the lever L is in thenormal position N, as shown, contact i2engages contact i8 to which is connected control wire 10, while contactl4 engages contact H] to which is connected control wire ii. Accordinglyin this position of the control lever L current of one relativepolarity, which may be considered as normal polarity, is supplied frombattery l5 to control wires iii and H.

.When the lever L is in the reverse position R, contact it engagescontact l9, While'conta'ct. M engages contact 26 to which is" connecteda branch of control Wire it. Accordingly in this position oithe lever Lcurrent ofxthe opposite or reverse relative polarity is supplied frombattery it to the control wires VII and H.

Control wire it is connected to one terminal of the winding of relay WR,and also to one] terminal of the Winding of relay W'RP', while controlwire l l is connected to movable contact'ilt of overload relay OR.Contact 22, when released,

"engages contact 753 which is connected by wire 24 to neutral contact 25of relay andalso to movable contact 26 of relay WRP.

Contact 25 of relay WR, when released,

gages contact 32 which is connected by wire to movable contact 34* ofrelay 'WRP, to stationary contact of relay WRP and also to a terminal ofthe winding of relay WRR. Contact 26 of relay WRP, when picked up,engages contact.

35 tothereby establish connection from wire 2a to wire leading te -thewinding of relay JEEP, i while contact t l of relay WRP picked upengages contact 3b which is comiected by wire 29; to a terminal of, thewinding of relay WR.

. The relay WR, has neutral contacts M! which are connected. by wire Mto the normal polar con-tact Aland. to reverse polar contact 43 of therelay. Neutral contacts 49, when picked. up, en

gage contacts 45 which are'connected by wire it to contacts 48 of relayWRP. i

The contacts 63' and d5 of relay lit/R. operate, as hereinafterexplained in detail, in the event of an overload of the switch andresultant picking up of the contacts of overload relay OR, or in theevent of reversal of the switch in mid stroke, to interrupt the switchmotor circuit. It desired that the contacts. 4!! and 45 be constructedof rnetal, and the system provided by this invention is directed tomeans to prevent injury to the motor, and to prevent subsequent improperoperation of the motor and of the associated apparatus, in the event thecontacts so and is of relay WR fuse together and fail to separate ondeenergization of the winding of the relay.

The contacts d8 of relay WRP, when picked up, engaged contacts 49 whichare connected by wire iii! to terminal C of battery 52. The contacts 48and 49 may either or both be constructed of infusible material so thatthese contacts cannot fuse together and fail to separate.

The relay WR has a polar contact 53 which is connected by wire 55 toresistance unit and to one terminal of the pick-up winding 58 ofoverload relay OR. The other terminals of the resistanceunit 56 and ofthe winding 58 oirelay The relay WR, also has a polar contact 65 whichis connected bywire 66 to the other brush of the motor armature 68.

Contact 65, when in the normal position, as shown, engages contact d2,while, whenit is in Kits reverse position, contact 65 engages reversepolar contact til which is connected by wire 89 to contact 10.

The switch W has associated therewith a movable contact "if! which is"movable in accordance with movement of the switch and which at timesengages the contacts 64 and 7B. The contacts 64 and 1E! are arranged sothat contact '52 engages contact 54 in all positions of the switch Wexcept the normal position. thereof, while contact I2 engages contact"it in all positions of the switch nected by wire it to terminal B ofbattery 52.

The overload relay OR has a holding winding H to one terminal of whichis connected a branch of control wire I'd, while the other terminal ofthis winding. is connected by wire Hi to contact that the relay. Contactllil, when released, en-

gages a contact 8! to which is connected wire Hi to thereby estabiish acircuit shunting: the holding winding l! and thus render the overloadrelay slow'acting. The circuit shunting the windi'i traced fromone-terminal of the winding through wire 'Fl, contacts 3E-Sl, and wireI0 to the other terminal of the relay winding.

On picking up of contact lib of relay OR, the contact as first becomesdisengaged from contact M to interrupt the circuit shunting the windingH, while on further movement of the contactiii! it engages contact. 22to thereby establish. the circuit for energizing the holding winding 11from the control wires it and H. On still. further upward movement ofthe contact 8!! contact 22is moved out of engagement with contact 23 tothereby interrupt connection from control wire H to wire 2d, and thusinterrupt energization of the windings of relays WR and WRP.

The resistance unit 56 has a positive thermal coeflicient of resistance,that is. the resistance or the unit increases as the temperature of the-material of which the unit. is constructed increases. The resistanceunit 56 and the various parts of the overload relay OR, are arranged andproportioned sothat under normal conditions most of the current in thecircuit of the switch motor M flows through the resistance unit 56,while too little current flows through the pick-up winding 58 of relayOR to cause the contact 80 of the relay to become picked up. Accordinglycontact it!) normally remains released.

In the event of an obstruction to movement of the switch so that anunusually heavy current is present in the circuit of the switch motorfor an appreciable time interval, the materialof which the unit 55 isconstructed becomes heated and its resistance increases, therebyincreasing current in the pick-up winding 58 of relay to a valueefiective to cause picking upv of contact all.

The relay W'R may have polar contacts, not shown, which cooperate withswitch operated contacts, not shown, in the manner well known in theart, to control the supply of current, and also the polarity of thecurrent supplied, to circuits,such as wires Hi2 andlild, for indicatingthe position of the switch W.

The wire N12 is connected to contact I03 of OR the the relay WRP, whilewire I04 is connected to contact I05 of relay WRP. Contact I03, whenpicked up, engages a contact I06 to which is connected indication wireI'I, while contact I05, when picked up, engages contact I08 to which isconnected indication wire I06. The indication wires I01 and I09 lead tosuitable means, not shown, for indicating at a remote point, such as atthe point at which switch control lever L is located, the positionoccupied by the switch W.

The contacts of the relay WRP are slow in releasing so that when thewindings of the relays WR and WRP are simultaneously deenergized, orwhen the direction of energization of the windings of these relays issimultaneously reversed, the contacts 40 of relay WR will becomereleased and will interrupt the circuit of the switch motor M before thecontacts 48 of relay WRP become released. a

The equipment is shown in the drawing with the switch W and the switchcontrol lever L in their normal positions, with the windings of relaysWR and WRP energized, and with the contact 60 of overload relay ORreleased.

At this time as the switch control lever L is in the normal position,current of normal relative polarity is supplied from battery I to thecontrol wires I0 and II, and as the winding of relay WR is energizedwith current of normal relative polarity, the neutral contacts and 40 ofthe relay are picked up, while the polar contacts 53 and 65 of the relayare in their normal positions as shown. As the winding of relay WRP isenergized, the contacts of this relay are picked up.

The circuit for energizing the winding of relay WR from the controlwires I0 and II is traced from wire II through contacts 22-23 of relayOR, wire 24, contacts 26-35 of relay WRP, wire 33, contacts 34-30 ofrelay WRP, wire 29, and winding of relay WR to wire I0.

At this time the winding of the relay WRP is energized from the controlwires I0 and II over its stick circuit which is traced from wire IIthrough contacts 22-23 of relay OR, wire 24, contacts 26-35 of relayWRP, wire 33, winding of relay WRP, and wire I0.

As the switch W is in the normal position, contact I2 does not engagecontact 64, and hence the normal supply circuit for the switch motor isinterrupted.

If at this time the operator wishes to effect movement of the switch Wfrom its normal to its reverse position, he can do so by moving theswitch control lever L from its normal to its reverse position.

On this movement of the control lever L to the reverse position, currentof reverse relative polarity is supplied to the control wires I0 and II,and therefore to the windings of the relays WR and WRP. On this reversalin the direction of energization of the windings of reIays'WR and WRP,the neutral contacts of these relays become released, therebyinterrupting the previously traced circuits for energizing the relaywindings fromthe control wires I0 and II.

On release of contact 25 of relay WR, it engages contact 32 which isconnected by wire 33 to a terminal of the winding of relay WRP. Thewinding of relay WRP, therefore, is energized from the control wires I0and II over its pickup circuit which is traced from control wire IIthrough contacts 22-23 of relay OR, wire 24, contacts 25-32 of relay WR,wire 33, winding of relay WRP, and control wire I0.

On picking up of contact 26 of relay WRP it engages contact 35 tothereby establish the previously traced stick circuit for the winding ofrelay WRP.

On picking up of the contacts of relay WRP, contacts 26 and 34 establishthe circuit to energize the winding of the relay WR from control wiresI0 and II. This circuit is traced from wire I I through contacts 22-23of relay OR, wire 24, contacts 26-35 of relay WRP, wire 33, contacts34-30 of relay WRP, wire 23, winding of relay WR, and control wire I0.

At this time, therefore, the winding of relay WR will be energized withcurrent of reverse relative polarity, and as a result the polar contactsof this relay will be shifted from their normal to the reversepositions, while the neutral contacts of the relay will become pickedup.

On picking up of contact 25 of relay WR. the

pick-up circuit for the Winding of relay WRP is interrupted, but at thistime the winding of relay WRP is maintained energized by currentsupplied over its stick circuit.

On movement of the polar contacts 53 and 65 of relay WR to their reversepositions, and on picking up of the neutral contacts of the relay WR ata time when the contacts 48 of relay WRP are picked up, the reversesupply circuit for the motor M is established, and the motor is operatedto move the switch W from the normal to the reverse position. Thereverse supply circuit for the motor M is traced from terminal C ofbattery 52 through wire 50, contacts 49-48 of relay WRP, wire 46,contacts -40 of relay WR, wire 4I, contacts 43-53 of relay WR, wire 55,resistance unit 56 and pick-up Winding 58 of relay OR in parallel, wire59, motor armature 60, wire 66, contacts 65-68 of relay WR, wire 69,contact I0, switch operated contact I2, wire I3, motor field winding 15,and wire 16 to terminal B of battery 52.

On movement of the switch W to the reverse position, contact 12 is movedout of engagement with contact I0, thereby interrupting the circuit forenergizing the switch motor M with the result that the motor ceases tobe operated.

In similar manner if while the switch W is in the reverse position theoperator desires to move the switch to the normal position, he can do soby moving the control lever L from the reverse to the normal position.As a result of this movement of the control lever L, current of normalrelative polarity is again supplied to the control wires I0 and II.

On this reversal in the direction of energization of the control wiresI0 and II, and therefore of the windings of relays WR- and WRP, theneutral contacts of relay WR become released, while the contacts ofrelay WRP also become released. On

the release of the neutral contacts of relay WRP, the previously tracedcircuits for energizing the windings of relays WR and WRP from controlwires I0 and II are interrupted, while on release of contact 25 of relayWR, it engages contact 32 to establish the circuit from. wire 24 to wire33, and thus to complete the pick-up circuit for the winding of relayWRP so that the winding of relay WRP is energized. As a result ofenergization of the winding of relay WRP, the contacts of this relaybecome picked up, and on picking up of contact 34, the pick-up circuitfor the winding of relay WR is established. and the winding of relay WRis energized with current of normal relative polarity from the controlwires I0 and I I.

As a result of this energization of the winding of relay WR,the polarcontacts 53 and $5 of the relay are shifted to their normal positions,while the neutral contacts and it of the relay become picked up. Onpicking up of neutral contact 25 of relay WR, the pick-up circuit forthe winding of the relay WRP. is interrupted, but at this timethe'winding of relay WRP is maintained energized by current suppliedover its stick circuit which was established on picking up of contact26.

On picking up ofathe neutral contacts 40 of relay'WRand onrnovement ofthe polar contacts 53 and 65 of this relay to their normal positions ata time when the contacts of relay WRP are picked up, the normal supplycircuit for the switch motor M is established, and the motor is causedto move the switch W from the reverse to the normal position.

The normal supply circuit for the switch motor M is traced from terminalC of battery 52 through wire 59, contacts 49 l3 of relay WRP, wire 4'5,contacts lfi of relay WR, wire 4!, contacts 12-85 of relay WR, wire 65,motor armature 60, wire Bil, resistance unit 56 and overload relaypick-up winding 58 in parallel, wire I 55, contacts 536! of relay WR,wire 62, contact 64, switch operated contact l2, wire l3, motor fieldwinding 75, and wire "it to terminal B of hat contact a: to therebyinterrupt the normal supply circuit for the switch motor and thusprevent further operation of the motor.

If, While the switch W is being moved from one of its positions to theother, as, for example, from the normal to the reverse position, theoperator desires to return the switch to its original position, in thiscase the normal position, he may do so by returning the control lever toits normal position.

As it is assumed that the switch W is being moved to the reverseposition, the control lever L is in its reverse position and current ofreverse relative polarity is supplied from battery It to the controlwires ill and H, while the neutral and polar contacts of relay WR andthe contacts 48 of relay WRP establish the previously traced reversesupply circuit ior the motor M.

On movement of the lever L to the normal position, current of normalrelative polarity is supplied to the control Wires H3 and it, while onthis change in the polarity of the current supplied to the wires Hi andH, the neutral contacts of the relays WR and WRP become released andinterrupt the circuit of switch motor. Because of the slow releasingcharacteristic of the contacts of that-relay WRP, the contacts 46 ofrelay WR release before the contacts of relay WBP release, and hence thecircuit of the switch motor is first interrupted by the contacts it, andis thereafter interrupted at another point by the contacts d8 of therelay WEP.

.As the contacts to of relay WR become released before contacts 43 ofrelay WRP become released the circuit of the switch motor is interruptedby contacts 46 of relay WR, so that on release of contacts 48 of relayWR no arcing or burning of the contacts 48 and 455 of relay WRP occurssince the circuit or" the switch motor is already interrupted bycontacts 40 of relay WR.

0n release of contact 25 of relay WR, the pickup circuit for energizingthe winding of relay WRP is established, while on picking up of thecontacts of relayWRP, the circuit for energizing the winding of relay WRis established. In addition, on picking up of the contacts of relay WRPthe stick circuit for-energizing therelay winding is established so thaton subsequent pickingllp: of the neutral contact 25' of relay WR,thewinding of relay WRP is maintained energized.

As a result of the energization. of the winding of relay WR followingestablishment of the ener-v gizing circuit for this :relay winding, thepolar contacts 53 andv ers shifted to their normal positions, while theneutral contacts 25 and 40, of the relay become picked upv with theresult that the previously traced normal supply circuit for the-switchmotor M is established, and the motor operates to move the switch W tothe normal position. When the switch attains the normal position,contact 12 is moved out of engagement with contact St te interrupt thecircuit of the switch motor.

It will be seen that on energization of the winde ing of relay WRPcontacts 48 and 49 of this relay become. closed, but at this time thewinding of relay WR is deenergized and contacts 40 of relay WE arereleased. I-Ience at thetime of closing of contacts-48 and 49 of relayWRP no'current is flowing in the circuit controlled by these contacts,and, accordingly, no arcing or burning of these contacts occurs.

Furthermore, on subsequent picking up of the contacts 4'0 of relay WR tocomplete the circuit of the switch motor M, the contacts and 49 of relayWRP are firmly in engagement so that no arcing between these contactsoccurs.

The equipment operates in similar manner if, while the switch W is beingmoved from the reverse to the normal position, the operator decides toreturn it to the reverse position. At such times as a result of thereversal in the direction of energization of the control wires l0 and Il the neutral contacts of the relays WR and WRP become re-- leased tointerrupt the circuit of the switch motor, while subsequently thecontacts of these relays become picked up to reestablish the reversesupply circuit for the switch motor.

As pointed out above the contacts of relay WR release before thecontacts of relay WRP become released, While the-contacts of relay WR donot become picked up until the contacts of relay WRP are picked up. 7

If, while the switch W is being moved from one of its positions to theother, as for example from the normal to the reverse position, movementof the switch is obstructed so that the switch cannot complete itsmovement, the overload relay OR will be operated to interrupt thecircuits of the windings of the relays WR and WRP with the result thatthe neutral contacts of these relays will become released, and willinterrupt the circuits of the switch motor Mand thereby prevent injuryto the motor.

For the purposes of illustration, it will be as sumed that the switchWis being moved from the normal to the reverse position, andthat fur-,ther movement of the switch is prevented before the switch reaches thereverse position.

When movement of the switch W is obstructed, the switch motor M draws anabnormally heavy current and the continued flow of this unusually heavycurrent in the circuit of the switch motor heats the material of whichthe resistance unit 56 is constructed, thereby increasing its resistanceand increasing the flow of current in the pick-up winding 58 of therelay OR.

When this abnormally. heavl current flow in the circuit of the switchmotor has continued for a predetermined time interval, the contact of.

relay OR becomes picked up, thereby interrupting the circuit shuntingthe holding winding 11. On further upward movement of the contact 80, itengages contact 8| to thereby establish a circuit for energizing theholding winding 11 from the control wires 10 and H. This circuit istraced from control wire l0, through winding 11, wire 19, contacts 8022of relay OR, and control wire H.

The various parts of the apparatus are arranged so that on energizationof the holding winding H with current of the polarity supplied at thistime from the control wires ID and I I, this winding assists the pick-upwinding 58 to effect picking up of the contact 80, and, accordingly, thecontact 80 is moved further towards the picked up position.

On this further movement or contact 80, con tact 22 is moved out ofengagement with contact 23, thereby interrupting connection from controlwire II to wire 24, and thus interrupting the energizing circuits forthe winding of relay WR and also for the winding of relay WRP.

On deenergization of the windings of relays WR and WRP occasioned byseparation of contacts 22 and 23 of relay OR, because of the slowreleasing characteristic of relay WRP, the neutral contacts 40 of relayWR become released before the contacts 48 of relay WRP become released.Accordingly contact 40 of the relay WR. interrupts the circuit of theswitch motor M and thus prevents injury to the motor which might resultfrom continued energization thereof at a time when movement of theswitch W is obstructed.

On subsequent opening of the contact 48 of relay WRP, the circuit of theswitch motor has already been interrupted, and hence no arcing orburning of these contacts occurs.

' At this time, following interruption of the switch motor circuit bythe relays WR and WRP, the contact 80 of overload relay OR continues tobe maintained picked up by the holding winding 11, which is energized bycurrent supplied from the control wires l0 and II over the circuitestablished by contacts BIL-22 of the relay.

On the occurrence of the obstruction to movement of the switch W andoperation of the overload relay OR to cause the relays WR and WRP tointerrupt the switch motor circuit, the operator may thereafter returnthe switch W to the position from which it was being moved when movementof the switch was obstructed.

-In this example, the switch is to be returned to the normal position,and to effect this movement of the switch the control lever L is movedfrom its reverse to its normal position.

On this movement of the control lever L to the normal position, there isa reversal in the direction of energization of the control wires and H,and, therefore, in the direction of energization of the holding winding1? of the overload relay OR.

On this reversal in the direction of energization of the winding 11, thecontact 80 of over- :load relay OR becomes released, thereby inter--rupting the circuit for energizing the holding Winding 11, while contact8B again engages contact 8| to establish the circuit shunting theholding winding. On release of contact 80 and re sultant movement of thecontact out of engagement with contact 22 to interrupt the circuit forenergizing holding winding H, the winding will not thereafter againbecome energized and hence the contact 80 will remain released.

load relay OR, contact 22 is moved into engagement with contact 23 tothereby establish connection from control wire H to wire 24. At thistime since the contact 25 of relay WR, is released connection isestablished from wire 24 to wire 33 leading to one terminal of thewinding of auxiliary relay WRP, and, accordingly, the winding of relayWRP is energized and the contacts of this relay become picked up andestablish the stick circuit for the relay winding.

0n picking up of the contacts of relay WRP, the energizing circuit forthe winding of relay is established and contacts of relay WR becomepicked up, while as the relay winding is energized with current ofnormal relative polarity, the polar contacts of the relay are shifted totheir normal positions to thereby complete previously traced normalsupply circuit for the switch motor M.

In addition on picking up of the neutral contact 25 of relay WR, thepick-up circuit for the winding of relay WRP is interrupted.

On completion of the normal supply circuit for the switch motor M, themotor is operated to return the switch W to the normal position, thatis, to move the switch W away from the obstruction which prevented itsmovement to the reverse position. When the switch W attains the normalposition, contact '52 moved out of engagement with contact 64 tointerrupt the circuit of the switch motor.

It will be seen that in the event or" an overload of the switch motorand resultant operation of the overload relay, the contacts 48 of therelay WR become released before contacts 48 of relay WRP becomereleased. This sequence of operation takes place because the contacts ofthe relay WRP are slow in releasing.

Since the neutral contacts of relay WR release before the contacts ofrelay WRP become released, the switch motor circuit is interrupted bythe contacts of relay WR and not by the contacts of relay WRP.

In like manner, on subsequent completion oi the circuit of the switchmotor, either following an overload or during normal operation of theequipment to effect movement of the switch, the contacts of relay WRPbecome picked up before the neutral contacts of relay WR become pickedup, and hence the circuit of the switch motor is incomplete at the timethe contacts 53 of relay WRP engage contacts 49. Accordingly no arcingor burning of these contacts will result.

The equipment operates in a similar manner in the event of an overloadwhen the switch W is being moved to the normal position. At this timethe overload relay OR will operate as previous y described to interruptthe energizing circuits of the windings or relays WR and WRP, and theserelays will operate to interrupt the switch motor circuit. On subsequentmovement of the switch control lever L to the reverse position, thecontact of the overload relay OR becomes released and reestablishes' thecircuits for energizing the windings of relays WR and WRP, and theserelays operate as previously described to establish the reverse supplycircuit for the switch motor M with the result that the motor returnsthe switch W to the reverse position.

In the event the neutral contacts 40 and of relay WR fuse together sothat they fail to separate when they should separate, this systemopcrates in such manner that the winding of relay WRP cannot thereafterbe energized, and, ac-

As a result of the release of contact 80 of overcordingly, the contactsof relay WRP remain released to interrupt the circuit of the switchmotor, and to also prevent energization of the Winding of relay WR tothereby prevent a change in the position of the polar contacts of relayWR. As previously pointed out, the neutral contacts of relay WR shouldbecome released when the polarity of the current supplied to the controlwires Ill and H is changed, or when the circuit of the relay winding isinterrupted by operation of the overload relay OR.

For purposes-of illustration, it will be assumed that the neutralcontacts l and ti: of relay WR fuse together at a time when the relaywinding is energized with current of normal relative polarity, and thaton the subsequent supply of current of reverse relative polarity to thecontrol wires Hi and i I, the contacts of relay WR fail to separate.

On a change in the polarity of the current supplied to control wires illand ii, there is a reversal in the direction of energization of thewinding of relay WRP and the neutral contacts of this relay becomereleased.

On release of contact 26 of relay WRP, connection from wire 24 to wire(it is interrupted, there-- by interrupting the stick circuit for thewinding of relay WRP. At this time, as it is assumed that the neutralcontacts l0 and oi relay WE. are fused together, the neutral armature ofthe relay will be held in its picked-up position and contact 25 will beheld out of engagement with contact 32 so that the pick-up circuit forthe winding of relay WRP is interrupted. Accordingly on release of thecontacts of relay WRP,

the'circuit for energizing the relay winding is interrupted, and henceonce the relay contacts are released, they will not thereafter againbecome picked up until contact 25 of relay WE becomes released.

On release of the contacts of relay WRP the circuit for energizing thewinding of relay WR is interrupted. Accordingly on the supply of currentof reverse relative polarity to the control wires and H, the winding ofrelay WR, will not be energized with current of reverse rela tivepolarity and the neutral contacts of the relay will remain in theirnormal positions.

As long as the neutral contacts of relay WR. remain fused together, and,therefore, remain in their picked up positions so that contact is heldout of engagement with contact 32, the winding of relay WRP cannot beenergized, and hence the contacts 48 of this relay will remain releasedand will interrupt the circuit of the switch motor.

In addition contacts I03 and 1050f the relay WRP will be released andwill interrupt the supply .of current to the indication wires I01 andI09 and the indication means controlled by these wires will fail toprovide an indication and the operator will thereby be informed that theequipment is not functioning in the intended man- In order to restorenormal control of the switch W to the control lever L, it is necessaryto first separate the neutral contacts of relay WR and thereby causecontact 25 to engage contact 32 and thus establish the pick-up circuitfor the winding of relay WRP. The contacts'of relay WRP will thereuponbecome picked upand will establish the circuit for energizing thewinding of relay WR, While the equipment will thereafter operate in themanner described in detail above.

The apparatus operates in a similar manner if on picking up of contact80 of overload relay OR, the neutral contacts of relay 'WR fail "toseparate. Under these conditions, on picking up of contact of relay OR,the windings of relays WR and WRP will be deenergized. The contacts ofrelay WRP will become released andoontacts 4.8 of the relay willinterrupt the circuit of the switch motor and thus preventinjury to theswitch motor.

on subsequent reversal in the polarityof the current supplied to thecontrol wires l0 and H, the contact 80 of relay OR becomes released andreestablishes connection from control wire II to wire 24. As the neutralcontacts of relay WR are assumed to be held in their picked-uppositions, contact 35 of relay WR will be maintained picked up therebyinterrupting the pick-up circuit for the winding of relay WRP.Accordingly: the winding of relay WRP will remain deenergized and willmaintain the circuit of the switch motor interrupted. As explainedabove, the contacts of relay WRP will remain released until the constact 25 of relay WR. is released.

It will be seen that the auxiliary relay WRP employed in the systemprovided by my invention checks the release of the neutral contacts ofrelay WR, and, if for'any reason the neutral contacts of relay WR failto releasewhen they should, the contacts of relay WRP will interrupt themotor circuit and prevent further operation of the switch motor untilthe relay WR is caused to function in the intended manner.

It will be seen also that under normal operating conditions, when all ofthe equipment is functioning as intended, the circuit of the switchmotor is interrupted by the switch operated contact l2 and theassociated stationary contacts. In the event of operation of theoverload relay OR or in the event the switch is reversed when in midstroke, the circuitcf the switch motor is interrupted by the neutralcontacts 49 and 45 of the relay WR. The contacts 40 and of relay WE, areconstructed of metal and are adapted to be employed to interrupt thecircuit of the switch motor.

The neutral contacts 48-49 of relay .WRP, which are constructed ofinfusible material, ordinarily do not interrupt the circuit of theswitch motor when current is present in this circuit. Accordingly noarcing or burning or other injury occurs to these contacts. In the;event, however, the neutral contacts of relay WR fuse together and failto separate when they should, the contacts 48 and d9 of relay WRP willinterrupt the switch motor circuit, but this willbe so infrequent thatthe damage to the contacts will be negligible.

Although I have herein shown and described only one form of motorcontrol system embody ing my invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of myinvention. 7

Having thus described my invention, what I claim. is:

1. In a motor control system, in combination, an electric motor, a firstrelay and a second relay, a supply circuit including contacts of both ofsaid relays for energizing said motor, said relays being operable whenenergized to establish said supply circuit and being operable whendeenergized to interrupt said supply circuit, and common means forenergizing said relays, the contacts of the first relay beingconstructed of fusible material, the contacts of the second relay beingformed of material such that the contacts are infusible, the relaysbeing arranged and proportioned so that when both are simultaneouslydeenergized the contacts of the second relay will remain closed untilafter the contacts of the first relay are separated.

2. In a motor control system, in combination, an electric motor, a firstrelay and a second relay, a supply circuit including contacts of both ofsaid relays for energizing said motor, a control circuit for energizingsaid relays, and means for supplying current to said control circuit,the contacts of the first relay being formed of fusible material, thecontacts of the second relay being formed of material such that thecontacts are infusible, the relays being arranged andproportioned sothat on a variation in the current in the control circuit to effectopening of the relay contacts the contacts of the second relay willremain closed until after the contacts of the first relay become opened.

3. In a motor control system, in combination, an electric motor, a firstrelay and a second relay, a supply circuit including contacts of both ofsaid relays for energizing said motor, said relays being operable whenenergized to establish said supply circuit and being operable whendeenergized to interrupt said supply circuit, a control circuit forenergizing said relays, and means for supplying current to said controlcircuit, the contacts of the first relay being formed of fusiblematerial, the contacts of the second relay being formed of material suchthat the contacts are infusible, the relays being arranged andproportioned so that when both are simultaneously deenergized thecontacts of the second relay will remain closed until the contacts ofthe first relay become opened.

4. In a motor control system, in combination, an electric motor, a firstrelay anda second relay, a supply circuit including contacts of both ofsaid relays for energizing said motor, said relays being operable whenenergized to establish said supply circuit and being operable whendeenergized to interrupt said supply circuit, a control circuit forenergizing said relays, and means for supplying current to said controlcircuit, the contacts of the first relay being formed of fusiblematerial, the contacts of the second relay being formed of material suchthat the contacts are infusible, the contacts of the second relay beingslow in releasing so that when said relays are simultaneouslydeenergized the contacts of the second relay will not become openeduntil after the contacts of the first relay have become opened.

5. In a motor control system, in combination, an electric motor, a firstrelay and a second relay, a supply circuit including contacts of both ofsaid relays for energizing said motor, said relays being operable whenenergized to establish said supply circuit and being operable whendeenergized to interrupt said supply circuit, a control circuit throughwhich current may be supplied to energize said relays, means forsupplying current to said control circuit, a pick-up circuit forenergizing the second relay from said control Wires, said circuit beingcontrolled by a contact of the first relay and being complete when andonly when the contacts of the first relay are released, a stick circuitfor energizing the second relay from said control circuit, said stickcircuit being complete when and only when the contacts of the secondrelay are picked up, and a circuit including a contact of the secondrelay for energizing the first relay from said control circuit, saidcircuit being complete when and only when the contacts of the secondrelay are picked up, the contacts of the second relay being slow inreleasing so that when the relays are simultaneously deenergized thecontacts of the second relay will not become released until after thecontacts of the first relay become released.

6. In a motor control system, in combination, an electric motor, apolarized relay having neutral and polar contacts, a neutral relay, asupply circuit including neutral contacts of the polar relay andcontacts of the neutral relay for energizing said motor, the polarcontacts of the polar relay also controlling the supply circuit toeffect operation of the motor in one direction or the other, a controlcircuit through which current may be supplied to energize said relays,means for supplying current of one polarity or the other to said controlcircuit, a pick-up circuit for energizing the neutral relay from saidcontrol circuit, said pick-up circuit being controlled by a neutralcontact of the polar relay and being complete when and only when saidcontact is released, a stick circuit for energizing the neutral relayfrom said control circuit, said stick circuit being controlled bycontacts of the neutral relay and being complete when and only when saidcontacts are picked up, and a circuit complete when and only when thecontacts of the neutral relay are picked up for energizing the polarrelay from said control circuit, the contacts of the neutral relay whichcontrol the motor supply circuit being formed of material such that theyare infusible, the neutral contacts of the polar relay which control themotor supply circuit being formed of fusible material, the contacts ofthe neutral relay being slow in releasing so that when both relays aresimultaneously deenergized or when the polarity of the current suppliedto said control circuit is changed the contacts of the neutral relaywill remain closed until after the neutral contacts of the polar relaybecome released.

7. In a motor control system, in combination, an electric motor, apolarized relay having neutral and polar contacts, a neutral relay, asupply circuit including neutral contacts of the polar relay andcontacts of the neutral relay for energizing said motor, the polarcontacts of the polar relay also controlling the supply circuit toeffect operation of the motor in one direction or the other, a controlcircuit through which current may be supplied to energize said relays,means for supplying current of one polarity or the other to said controlcircuit, and means for energizing said relays with current supplied fromsaid control circuit, the contacts of the neutral relay which controlthe motor supply circuit being formed of material such that the contactsare infusible, the neutral contacts of the polar relay which control themotor supply circuits being formed of fusible material, the contacts ofthe neutral relay being slow in releasing so that when the relays aresimultaneously deenergized or when the polarity of the current suppliedto the control circuit is changed the contacts of the neutral relay willremain closed until the neutral contacts of the polar relay becomeopened.

8. In a motor control system, in combination, an electric motor, apolarized relay having neutral and polar contacts, a neutral relay, asupply circuit including neutral contacts of the polar relay andcontacts of the neutral relay for enersaid motor, the polar contactsofthe polar relay also controlling the supply circuit to efiect operationof the motor in one directionhor the other, a control circuit throughwhich current may be supplied to energize said relays, means forsupplying current of one polarity or the other to said control circuit,means for energizing said relays with currentsupplied from said controlcircuit, and an overload relay governed in accordance with themagnitudeof the current flowing in said supply circuit, said overloadrelay controlling said control circuit, thecontact-s of the new tralrelay which control the motor supply circuit being formed of materialsuch that the contacts are infusible, the neutral contacts of theicolarrelay which control the motor supplycircuit belugs-formed of fusiblematerial, the contacts of the neutral relay lacing slow in releasingthat when the relays are .simultaneousiy deenergised or when thepolarity of the current supplied to the control circuit is changed thecontacts of the neutral relay will remain closed until the neutral.contacts of the polar relay become opened.

9. In a motor control system,in combination, an electric motor, a firstrelay and a second relay, a supply circuit including contacts of both ofsaid relays for energizing said motor, a control circuit for energizingsaid relays, :rneans for supplying current to said control circuit, andan overload relay governed inaccordance with the magnitude of thecurrent flowing in said supply circuit, said overload relay controllingsaid con trol circuit, the contacts of the met relay being formed offusible material, the contacts oi the second relay being formed ofmaterial such that the contacts are infusible, the relays being arrangedand proportioned so that on a variation in the current in the controlcircuit to effect opening of the relay contacts the contacts of thesecond relay will remain closed until after the contacts ofthe firstrelay become opened.

l0. In a motor control system, in combination, an electric motor, afirst relay and a second relay, a supply circuit including contacts orboth of said relays for energizing said motor, said relays beingoperable when energized to establish said supply circuit and beingoperable when deencr that when both are simultaneously. dcenergizedthefcontacts of the second relay will remain closed until after thecontacts of the first relay are separated.

' CLAUDE M. IHNES.

